Pre-equilibrium chemical reaction energy converter

ABSTRACT

The use of newly discovered chemical reaction products, created when reactants combine to form products on the surface of a catalyst, to generate electricity, beams of radiation or mechanical motion. The invention also provides methods to convert the products into electricity or motion. The electric generator consists of a catalyst nanocluster, nanolayer or quantum well placed on a substrate consisting of a semiconductor diode, and a semiconductor diode on the surface of the substrate near the catalyst. The device to generate mechanical motion consists of a catalyst nanocluster, nanolayer or quantum well placed on a substrate, and a hydraulic fluid in contact with the non-reaction side of the substrate, with the surfaces of both the catalyst and substrate mechanically formed to enhance the unidirectional forces on the fluid. Both devices use a fuel-oxidizer mixture brought in contact with the catalyst. The apparatus converts a substantial fraction of the reaction product energy into useful work during the brief interval before such products equilibrate with their surroundings.

CROSS REFERENCE TO RELATED APPLICATION(S)

This is a continuation of copending U.S. patent application Ser. No.09/589,669 filed on Jun. 7, 2000 now U.S. Pat. No. 6,327,859 which is aDivisional Application of U.S. patent application Ser. No. 09/304,979filed May 4, 1999, now U.S. Pat. No. 6,114,620.

FIELD OF THE INVENTION

The present invention relates to the extraction of electrical ormechanical energy or coherent radiation from chemical reactionsoccurring on the surface of a catalyst before thermal equilibrium hasbeen reached by the forms of the released energy.

BACKGROUND INFORMATION

Recent experimental observations have revealed clues to variouscatalytic processes occurring: 1) during the 0.01 picosecond timeinterval during which chemical reactants form bonds with the surface ofa catalyst, causing the emission of charge carriers, such as electronsand holes; 2) during the picosecond time interval during which reactantsadsorb and lose energy in quantum steps after becoming trapped at apotential well between an adsorbate and a catalyst surface, producingelectronic friction, charge carrier currents and phonon emission; and 3)during the nanosecond and longer time intervals during which reactionintermediates and products radiate electromagnetic energy, either whiletrapped on a catalyst surface or immediately after escaping it. Theseprocesses entail three energy releasing processes, namely: 1) chargecarrier emission (electrons and holes), 2) phonon emission and 3) photonemission.

The discovery of these pre-equilibrium emissions provides new pathwaysto convert the high grade chemical energy available duringpre-equilibrium phases into useful work. The term “pre-equilibrium”refers to the period, however brief, during which the products ofreactions have not yet come to thermal equilibrium. These productsinclude energy emissions, such as charge carriers; high frequencyphonons normally associated with the optical branch lattice vibrationsand with acoustic branch vibrations of similar wavelength and energy;and excited state chemical product species.

Prior to the discovery of these rapid energy emission pathways, theenergies resulting from a catalytic process, such as the heat ofadsorption and the heat of formation, were considered to be heatassociated with an equilibrium condition. Indeed, after tens offemtoseconds, emitted charge carriers have thermalized and after a fewto hundreds of picoseconds, emitted phonons have thermalized.

SUMMARY OF THE INVENTION

In an exemplary embodiment of the present invention, the emissions ofcharge carriers, such as electron-hole pairs, generated by chemicalactivity and reactions on or within catalyst surfaces, clusters ornanoclusters, are converted into electric potential. In an exemplaryembodiment, semiconductor diodes such as p-n junctions and Schottkydiodes formed between the catalyst and the semiconductors are used tocarry out the conversion. The diodes are designed to collect ballisticcharge carriers and can be Schottky diodes, pn junction diodes or diodesformed by various combinations of metal-semiconductor-oxide structures.The interlayer oxide thickness is preferably less than the particularballistic mean free path associated with the energy loss of theappropriate charge carrier (e.g., hole or electron). The diodes areplaced in contact with or near the catalyst nanolayer or nanoclusterwithin a distance whose order of magnitude is less than approximatelythe mean free path of the appropriate ballistic charge carrieroriginating in the catalyst. In one embodiment, the diode is locatedadjacent to the catalyst cluster, while in a further embodiment, thediode is located under the catalyst, as a substrate.

The charge carriers travel ballistically over distances that can exceedthe width of appropriately fabricated semiconductor junctions, similarto a thermionic effect. However, unlike the thermionic effect, thecharge carriers in the case of the present invention need not haveenergy greater than the work function of the material involved. Thecharge carrier motion is trapped as a difference in fermi level, orchemical potential, between either side of the junction. The resultingvoltage difference is indistinguishable from that of a photovoltaiccollector. However, the charge carrier forces itself into the valence orconduction band and the circuit provides a counterpart hole or electron.

The present invention also provides devices and methods for convertingthe energy generated by catalytic reactions to mechanical motion beforethe energy thermalizes. In an exemplary embodiment, the converted motionis used to move a hydraulic fluid against a resisting pressure.

Recent advances in the art of quantum wells, atomically smoothsuperlattices and nanometer scale fabrication permit a degree oftailoring of the physical parameters to favor a particular reactionpathway (charge carrier, phonon, photon) or to enhance the efficiency ofthe energy collector.

The temperature of operation of a device in accordance with the presentinvention can be as low as hundreds of degrees Kelvin, which is muchlower than the typical operational temperatures of conventionalthermophotovoltaics and thermionic systems (1500 to 2500 Kelvin).Moreover, the power per mass and power per volume ultimately achievableusing pre-equilibrium emissions in accordance with the present inventionexceeds that of fuel cells, conventional thermo-photovoltaics, andconventional thermionic systems.

Furthermore, in comparison to fuel cells which require complex ducting,the devices of the present invention allow mixing of fuel and air in thesame duct, thereby simplifying ducting requirements.

The combination of high volume and mass power density, simplicity, andlower temperature operation makes the methods and devices of the presentinvention competitive and uniquely useful.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1. shows a cross-section of an exemplary embodiment of a device forgenerating electricity in accordance with the present invention.

FIG. 2 shows a cross-section of an exemplary embodiment of a device forconverting the energy released by a catalytic reaction into mechanicalwork.

FIG. 3 shows a cross-section of an exemplary embodiment of a device forgenerating electricity piezoelectrically.

FIG. 4 shows an exemplary embodiment of an arrangement for generatingelectricity or radiation beams in accordance with the present invention.

DETAILED DESCRIPTION

FIG. 1 shows a cross-sectional view of an exemplary embodiment of adevice in accordance with the present invention. The device of FIG. 1,includes a catalyst 105 which is arranged on a top surface of the deviceto come into contact with oxidizer molecules 103 and fuel molecules 102.In the exemplary embodiment of FIG. 1, the catalyst 105 can be comprisedof platinum or palladium, the oxidizer 103 can be comprised of air andthe fuel 102 can be comprised of hydrogen or a reactant hydrocarbon suchas methanol or ethanol. Exhaust molecules 104 result from the catalyzedreaction.

The exemplary device of FIG. 1 comprises a pair of Schottky diodes whichact as charge carrier collectors, with one diode 113 being arranged onthe top surface of the device, adjacent to the catalyst 105 (the“adjacent surface diode”) and the other diode 109 being arranged in thesubstrate 108, below the catalyst (the “substrate diode”). An insulatinglayer 111 is arranged between the adjacent surface diode 113 and thesubstrate 108, as shown. The diodes 109 and 113 preferably comprise abipolar semiconductor material such as InGaAsSb with a compositionchosen to optimize the chosen operating conditions. For example, thesecond harmonic of a CO stretch vibration on a catalyst surface at 2340per cm energies gives a photon energy of 0.58 eV. (This matches the 0.53eV band gap of a recently developed InGaAsSb diode described in G. W.Charache et al., “InGaAsSb thermophotovoltaic diode: Physicsevaluation,” Journal of Applied Physics, Vol. 85, No. 4, February 1999).The diodes 109 and 113 preferably have relatively low barrier heights,such as 0.05 to 0.4 volts.

The substrate diode 109 should be forward biased sufficiently (e.g., upto 3 volts) to raise its conduction and valence bands above the fermilevel of the catalyst 105 so as to match the energy levels of theadsorbed reactants on the catalyst surface, such as oxygen orhydrocarbon free radicals. This induces resonant tunneling of energyinto the substrate diode 109 by photons. The dimension of the oxidebarrier or the depletion region should be kept to less than theballistic transport dimension, which is on the order of 10 nanometers.

A metal such as Mg, Sb, Al, Ag, Sn Cu or Ni may be used to form aninterlayer 106 between the catalyst 105 and the semiconductor of thesubstrate diode 109. The interlayer 106 serves to provide a latticeparameter match between the catalyst material and the substrate, whichin turn provides a smooth and planar interface surface with which toconstruct a quantum well structure consisting of the catalyst, thevacuum above and the interlayer below. A quantum well structure withsmooth interfaces alters the density of electron states in thedirections toward the substrate and toward the vacuum, so as to enhancethe number of electrons with the desired energy. The thickness of thecatalyst and the interlayer should be small enough to permit ballistictransport of charge carriers. This dimension is typically less than 20nanometers. Quantum well structures with thickness less than 0.5nanometer are possible in the present state of the art. The quantum wellstructure may be constructed as an island, like a pancake on a surface(also referred to as a “quantum dot”).

The device of FIG. 1 may also include a non-conducting layer 107arranged between the substrate diode 109 and the catalyst 105. The layer107, which can be comprised of an oxide, permits forward-biasing of thediode 109 without a significant increase in the forward current. Thelayer 107 provides a barrier against such forward current. An optionaloxide 114 barrier may also be arranged on the surface of the devicebetween the catalyst 105 and the surface diode 113.

Electrical contacts 101, 110 and 112 are arranged as shown in FIG. 1.Contacts 101 and 110 serve as electrical output leads for the substratediode. Contacts 101 and 112 are the electrical output leads for thesurface diode.

In the device of FIG. 1, the catalyst layer 105 may comprise a quantumwell structure (including quantum dots) having a thickness typicallyless than 20 nm and being sufficiently small so as to alter the densityof electron states in the catalyst to favor the production ofsubstantially monoenergetic holes or electrons. The substrate diode 109and the catalyst 105 may be separated by an interlayer 106 of metal thatpermits matching the lattice parameters of the catalyst to thisinterlayer. The catalyst 105 and interlayer 106 comprise the quantumwell. The interlayer 106 must be sufficiently thin so as to permitnon-energy changing electron transport into the diode. The thickness ofthe interlayer 106 should be preferably less than 20 nanometers.

In an exemplary embodiment of a device in accordance with the presentinvention, the substrate diode 109 comprises an n-type direct band gapsemiconductor with a band gap chosen to favor the emission of energeticelectrons.

In a further exemplary embodiment, the thickness or cluster size (ifarranged in clusters) of the catalyst layer 105 is sufficiently small soas to permit the appearance of band gaps, discrete electron states andcatalyst properties unlike the same material in bulk. In this case, thecatalyst 105 can be comprised, preferably, of gold, silver, copper, ornickel and be arranged as monolayer, 200 atom clusters.

FIG. 2 shows an exemplary embodiment of a device in accordance with thepresent invention in which the emissions of phonons generated byadsorbing and bonding reactions on or within catalyst surfaces, clustersor nano-structures are converted into hydraulic fluid pressure.

In accordance with the present invention, pressures generated by phononsdirected into a catalyst body on a first side of the catalyst body forma phonon wave which can be guided by the geometry of the catalyst (orsubstrate upon which the catalyst may be situated) so that the phononstravel to the other side of the substrate and impart a pressure onto afluid. The thickness of this travel should be less than the meandistance over which the direction of the phonon remains substantiallyunperturbed. The phonons arrive at an angle (a “grazing” angle) suchthat the directional and asymmetric pressure of the arriving phononsappears as wave motion on the other side of the catalyst body whichpushes against a fluid such as a liquid metal or sacrificial interface,causing it to move in a direction parallel to the bottom surface. Anapparent negative coefficient of friction between the wall and the fluidis exhibited due to the wave motion or directed impulses along thesurface of the bottom of the device.

The exemplary device comprises a substrate 202 with top and bottomsurfaces having a saw-tooth pattern, as shown in the cross-sectionalview of FIG. 2. The bottom surface is in contact with a hydraulic fluid204. As shown in FIG. 2, the substrate can be thought of as comprising aplurality of sub-structures 200 having rectangular cross-sections andarranged adjacent to each other at an angle with respect to thehydraulic fluid 204.

At the top surface of the substrate, each sub-structure 200 includes alayer 201 comprising a catalyst. On an exposed side surface betweenadjacent sub-structures, each sub-structure 200 includes a layer 202 ofmaterial which is inert with respect to the catalyst and the reactants.The body of each sub-structure is comprised of a substrate 203, whichalso acts as a phonon waveguide. Platinum can be used for the catalystlayer 201 and for the substrate 203 with air as the oxidizer, ethanol ormethanol as the hydrocarbon reactant fuel and water or mercury as thehydraulic fluid 204. The hydraulic fluid can also serve as a coolant forthe device, thereby permitting high power density operation.

The catalyst 201 and substrate 203 may be comprised of the samematerial, e.g., platinum. Other substrate materials may be used based onstructural considerations, manufacturability and/or impedance matchingso as to maximize the propagation of the phonon motion into thehydraulic fluid.

The thickness of the platinum catalyst layer 201 and substrate 203should be less than the energy-changing mean free path of optical branchphonons or high frequency acoustic branch phonons, which is at least oforder 10 nanometers and can be as large as one micron.

Nanofabrication methods can be used to form the sawtooth patterns on thesurfaces of the substrate 202, with the dimension of a unit of suchpattern being as large as 1 micron.

By depositing the inert layers 202 as shown, e.g., on the right-facingfacets of the saw-tooth pattern of the top surface, a preferentialdirection is thereby established for reactions and thus for phononpropagation, as indicated by the arrow in FIG. 2.

Acoustic, ultrasonic or gigahertz acoustic Rayleigh waves on thecatalyst side can be used to stimulate the reaction rate and synchronizethe emission of phonons. The waves increase the magnitude of the phononemission and cause coherent emission, greatly enhancing both the peakand average power.

In a further embodiment, a thin layer or layers of material are arrangedbetween the substrate and the fluid. These layers are comprised ofmaterials having acoustic impedances between that of the substrate 202and the hydraulic fluid 204, so as to maximize the transmission ofmomentum into the hydraulic fluid and minimize reflections back into thesubstrate 204. The material should be selected so that the bulk modulusand phonon propagation properties of the material cause the phononsemerging from the substrate to be transmittied substantially into thefluid with minimal reflection and energy loss.

In a further embodiment of a device in accordance with the presentinvention, the emissions of phonons generated by catalytic reactions areconverted into electrical current by piezo-electric effects withinmaterials as the phonons impact the materials. An exemplary embodimentof such a device is shown in FIG. 3.

The exemplary device of FIG. 3 comprises a catalyst layer 301 arrangedon a piezo-electric element 303, which is in turn arranged on asupporting substrate 304. The catalyst layer 301 can be implemented as ananocluster, nanolayer or quantum well. Electrical leads 302 areprovided at opposite ends of the piezo-electric element 303 across whicha potential is developed, in accordance with the present invention. Inthe exemplary embodiment of FIG. 3, the catalyst layer 301 comprisesplatinum, with air as the oxidizer and ethanol or methanol as thehydrocarbon reactant fuel. The piezo-electric element 303 can compriseany piezomaterial, including semiconductors that are not normallypiezoelectric, such as InGaAsSb. The lattice mismatch between thesemiconductor and the platinum produces a strain, commonly called adeformation potential which induces piezoelectric properties insemiconductors, or ferroelectric or piezoelectric materials with a highnonlinearity such as (Ba, Sr)TiO3 thin films, AlxGal-xAs/GaAs andstrained layer InGaAs/GaAs (111)B quantum well p-i-n structures.

Where the piezoelectric element 303 is comprised of a semiconductor, thesemiconductor becomes a diode element that converts photons intoelectricity, collects electrons as electricity, and converts phononsinto electricity.

In the exemplary embodiment of FIG. 3, as the reactants interact withthe catalytic layer 301, phonons generated by the reactions areconducted into the piezoelectric material 303. As a result, a potentialis induced in the piezoelectric material 303 at the electrical contacts302.

The geometry of the substrate 303 is preferably such as to focus phononsso as to enhance the nonlinearity of the piezoelectric element 303. Thisresults in self-rectification of the high frequency phonons. In anexemplary embodiment, the piezoelectric element 303 is preferably curvedand shaped like a lens or concentrating reflector so as to focus thephonons generated by the catalyst on to the piezoelectric material. Thefocusing of the phonons causes large amplitude atomic motions at thefocus. The atomic motions induced by this focusing cause thepiezoelectric material to become nonlinear, causing non-linear responsessuch as the generation of electricity in the material at the focus. Thisin turn results in the piezo-material becoming a rectifier of thephonon-induced high frequency current.

Acoustic, ultrasonic or gigahertz acoustic Rayleigh waves can be used onthe catalyst side of the exemplary device of FIG. 3 to stimulate thereaction rate and synchronize the emission of phonons, to enhance themagnitude of the phonon emission and to cause coherent emission, greatlyenhancing both the peak and average power delivered to the piezoelectricmaterial 303. Acoustic Rayleigh waves accelerate oxidation reactions onplatinum catalyst surfaces. Surface acoustic waves can be generated onthe surface of the catalyst 301 using a generator (not shown). Suchwaves may have acoustic, ultrasonic or gigahertz frequencies. TheRayleigh waves induce reactions so as to synchronize the reactions,which in turn synchronizes the emission of phonons. The result is apulsing bunching of the reactions, which enhances the power delivered tothe piezoelectric material 303.

The frequency of operation of the device of FIG. 3 is preferably in theGHz range and lower so that rectification of the alternating currentsproduced by the piezoelectric material 303 can be achieved withconventional means, such as with semiconductor diodes.

In a further exemplary embodiment of the present invention,electromagnetic radiation, such as infrared photons emitted by excitedstate products such as highly vibrationally excited radicals and finalproduct molecules, is converted into electricity photovoltaically.Stimulated emission of radiation is used to extract the energy from theexcited state products, such as highly vibrationally excited radical andreaction product molecules both on the catalyst surface and desorbingfrom it. The extracted energy appears in the form of a coherent beam ora super-radiant beam of infra-red or optical energy. The frequencies ofthe radiation correspond to fundamental (vibration quantum number changeof 1) or overtones (vibration quantum number change 2 or greater) of thenormal mode vibration frequencies of the reactants. Several differentfrequencies may be extracted simultaneously in this invention. While theresulting coherent beam is useful in its own right, this high intensitybeam can also be photovoltaically converted into electricity. Inaccordance with the present invention, such emissions are created byreactions on catalyst surfaces, and are accelerated by the use ofoptical cavities. FIG. 4 shows an exemplary embodiment of an electricgenerator for performing such a conversion.

The device of FIG. 4 comprises one or more substrates 401 upon which acatalyst 402 is arranged in a plurality of islands, nanoclusters,quantum well clusters or quantum dots. The catalyst clusters aresufficiently spaced apart (e.g., tens of nanometers or more) and thesubstrate is made sufficiently thin (e.g., less than a centimeter totaloptical thickness), so that IR absorbtion is mitigated at thefrequencies of specie emission. The assembly of catalyst clusters on thesubstrates 401 is substantially transparent to the reaction radiations.The catalyst 402 is preferably platinum or palladium. The devicepreferably comprises a plurality of substrates 401 stacked so as topermit a volume of reactions.

The catalyst-substrate stack 401/402 is enclosed in an optical cavityhaving a highly reflective element 403 and a less reflective element 404arranged as shown in FIG. 4. The optical cavity and thecatalyst-substrate stack 401/402 are preferably resonant to the reactionradiations or their overtones. The optical cavity can be used tostimulate overtone radiation, i.e., multipole radiation where the changein quantum number is 2 or more, to increase the energy of the radiation.The optical cavity preferably has multiple frequencies, as in aFabrey-Perot cavity, that are tuned to overtones of the speciefrequencies.

A fuel 407, such as hydrogen, ethanol or methanol and an oxidizer 408,such as air, are introduced into the optical cavity where they interactwith the catalyst-substrate stack 401/402. Lean mixtures of fuel can beused so as to minimize resonant transfer, exchange or decay of excitedstate vibrational energy to other specie of the same chemical makeup inthe exhaust stream, during the time these species are in the opticalcavity and the photovoltaic converter 405 collects the radiation andconverts it into electricity.

A stimulated emission initiator and synchronizer device 412 is used toinitiate and synchronize the emissions in the optical cavity. The device412 can be a commonly available stimulated emission oscillator and canbe coupled to the device of the present invention in known ways. Theoptical cavity can be designed in a known way to create stimulatedemission of radiation. A photovoltaic cell is typically not veryefficient in converting long wavelength IR photons (1000 to 5000 percentimeter) characteristic of the catalytic reactions. The high peakpower output of the device 412 remedies this situation and makes the IRphotovoltaic cell more efficient.

A photovoltaic converter 405 is placed outside the volume of thecatalyst-substrate stack 401/402 anywhere visible to the emittedradiation. Such a placement allows cooling the photovoltaic collector405 using known methods. The electrical output leads 406 of thephotovoltaic collector 405 can be coupled to an electrical energystorage device 411 via a diode 410. The output of the photovoltaicconverter 405 is in pulses with the pulse rate typically being greaterthan one megahertz. The electrical energy storage device 411 maycomprise, for example, a capacitor, super-capacitor or battery. Giventhe high frequency of the pulsed output, a capacitor used as the storagedevice 411 can be quite compact. The capacitor need only be large enoughto collect the energy of a single pulse. The energy stored in thecapacitor can thus be millions of times less than the energy deliveredby the converter 405 in one second.

The chemical reactants on the catalyst surface permit overtonetransitions because they are part of a “ladder” of transitions andstrongly polarized on the catalyst surface, which permits all thetransitions to have non-zero dipole radiation transition matrixelements. Also, the reactants have no rotational smearing associatedwith free molecules in a gas because they are attached to the surfaceand can not rotate. These features permit a near monochromatic overtonelight amplification by stimulated emission of radiation.

The electromagnetic energy radiated by the stimulation of species, as inthe embodiment of FIG. 4, can be formed, into high brightness,quasi-monochromatic, poly-chromatic radiations or coherent beams.

In each of the above described embodiments which include photovoltaicsemiconductors, the catalyst is preferably operated at a high surfacepower density, e.g., in excess of la watts per square centimeter or witha peak surface power density of at least one watt per square centimeter,to enhance the efficiency of the photovoltaic semiconductors.

What is claimed is:
 1. A method of generating energy comprising: using areactant to generate vibrationally energized species in the vicinity ofthe reactant; and converting vibrational energy of the vibrationallyenergized species into a useful form of energy before the vibrationallyenergized species reaches thermal equilibrium, the converting beingperformed using a nanolayer, nanocluster, quantum well, or combinationsthereof.
 2. The method of generating energy as claimed in claim 1,further including collecting the form of energy.
 3. The method ofgenerating energy s claimed in claim 1, wherein the using a reactantincludes using a catalyst to initiate a reaction to create thevibrationally energized species.
 4. The method of generating energyclaimed in claim 1, wherein at least some of energized species is incontact with the reactant.
 5. The method of generating energy a claimedin claim 1, wherein the form of energy includes one or more selectedfrom the group of phonons, electromagnetic energy, and electrons.
 6. Themethod of generating energy a claimed in claim 1, wherein theelectromagnetic energy is a photon.
 7. The method of claim 1, whereinthe converting is performed within several tens of nanometers of areaction of the reactant.
 8. The method of claim 1, further comprising:removing equilibrated species from the surface by using a catalyst. 9.The method of claim 1, wherein the vibrationally energized speciesinclude highly vibrationally energized species.